Error during parsing(Unsupported non-standard amino acid found: NAG )

Hello there!

I receive this error while trying to perform prodigy protein-protein on top pose structure obtained from HADDOCK.
What should I do to remove this error?any recommendations for online servers that remove such errors from PDB file?

Such a web server is call a simple ASCII text editor to remove the lines containing NAG…

Or under Linux:

`grep -v NAG input.pdb >output.pdb`